Abstract

The paper presents the results of mechanochemical synthesis of hydroxyapatite (HAP) with simultaneous substitutions of lanthanum (La{sup 3+}) for calcium ions and silicate ((SiO{sub 4}){sup 4−}-group) for the phosphate group with the substituent concentrations in the range 0.2–2.0 mol per HAP mol. The use of Si-substituted HAP as a coating material promotes accelerated osteosynthesis and osteointegration of implants into the bone tissue. The replacement of calcium ions by La{sup 3+} in the HAP structure plays an antimicrobial role preventing inflammatory processes. Annealing-induced variations in the lattice parameters of synthesized samples indicate the substituent incorporation into the HAP structure. It is known that complex compounds with lanthanides are used for cancer chemotherapy. In particular, La plays a key role in the course of treatment of injured defects of bone tissue. In addition, La-substituted HAP can be used for filling bone defects and coating implants in postoperational areas affected by bone cancer.

@article{osti_22608269,
title = {Lanthanum-silicon-substituted hydroxyapatite: Mechanochemical synthesis and prospects for medical applications},
author = {Chaikina, M. V., E-mail: chaikinam@solid.nsc.ru and Bulina, N. V., E-mail: bulina@solid.nsc.ru and Prosanov, I. Yu., E-mail: prosanov@mail.ru and Komarova, E. G., E-mail: katerina@ispms.tsc.ru and Sharkeev, Yu. P., E-mail: sharkeev@ispms.tsc.ru},
abstractNote = {The paper presents the results of mechanochemical synthesis of hydroxyapatite (HAP) with simultaneous substitutions of lanthanum (La{sup 3+}) for calcium ions and silicate ((SiO{sub 4}){sup 4−}-group) for the phosphate group with the substituent concentrations in the range 0.2–2.0 mol per HAP mol. The use of Si-substituted HAP as a coating material promotes accelerated osteosynthesis and osteointegration of implants into the bone tissue. The replacement of calcium ions by La{sup 3+} in the HAP structure plays an antimicrobial role preventing inflammatory processes. Annealing-induced variations in the lattice parameters of synthesized samples indicate the substituent incorporation into the HAP structure. It is known that complex compounds with lanthanides are used for cancer chemotherapy. In particular, La plays a key role in the course of treatment of injured defects of bone tissue. In addition, La-substituted HAP can be used for filling bone defects and coating implants in postoperational areas affected by bone cancer.},
doi = {10.1063/1.4960228},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1760,
place = {United States},
year = 2016,
month = 8
}

Fluoridated hydroxyapatite (FHAp) was successfully synthesized from the starting materials of CaCO{sub 3}, CaHPO{sub 4}.2H{sub 2}O, and CaF{sub 2} via a mechanochemical-hydrothermal route. X-ray diffraction, infrared spectroscopy, surface area measurements, and scanning electron microscopy identified the resultant powders as FHAp nanocrystals with the specific surface areas of up to 114.72 m{sup 2}/g. The mechanism study revealed that under such mechanochemical-hydrothermal conditions the formation reactions of FHAp were completed in two stages. The starting materials firstly reacted into a poorly crystallized calcium-deficient apatite and the complete incorporation of fluoride ions into apatite occurred in the second stage.

The present paper investigates the preparation of magnesium (Mg) substituted biphasic mixtures of different hydroxyapatite (HAP)/{beta}-tricalcium phosphate ({beta}-TCP) ratios through aqueous precipitation method. The concentrations of added magnesium (Mg) were varied with the calcium in order to obtain constant (Ca+Mg)/P ratios of 1.67 ranging from 1.62+0.05, 1.58+0.09 and 1.54+0.13, respectively. The as prepared powders were calcined at different temperatures to study the phase behaviour and thermal stability. The powders were characterized by the following analytical techniques: TG-DTA, X-ray diffraction and FT-IR. The results have shown that substitution of Mg in the calcium-deficient apatites resulted in the formation of biphasic mixturesmore » of different HAP/{beta}-TCP ratios after heating above 700 deg. C. The ratios of the formation of phase mixtures were dependent on the calcium deficiency in the apatites with the higher deficiency having the strongest impact on the increased formation of {beta}-TCP and the substituted Mg was found to stabilize the {beta}-TCP phase. - Graphical abstract: Role of Mg in the behaviour of calcium-deficient apatites during calcination to form biphasic mixtures.« less

LaAlO[sub 3] was chemically modified in order to ascertain the effects of substitution of larger cations on the compound's slight rhombohedral distortion from cubic symmetry--a property that often degrades the performance of LaAlO[sub 3] substrates for epitaxial high-temperature superconducting films. La[sub 1[minus]x]Sr[sub x]Al[sub 1[minus]x]Ti[sub x]O[sub 3] (x = 0.05, 0.10, 0.15, 0.25), La[sub 1[minus]x]Sr[sub x]Al[sub 1[minus]x]Zr[sub x]O[sub 3], La[sub 1[minus]x]Sr[sub x]Al[sub 1[minus]x]Mg[sub x]O[sub 3[minus]2x]F[sub 2x] and La[sub 1[minus]x]Sr[sub x]Al[sub 1[minus]x]Sc[sub x]O[sub 3[minus]x]F[sub x] (x = 0.05, 0.10, 0.15) were prepared in polycrystalline form and 1--2 mm single crystals of the Sr, Ti- and Sr,Zr-substituted systems were grown using a PbO-PbF[submore » 2]-B[sub 2]O[sub 3]-PbO[sub 2] flux. Shifts in the peak positions of the X-ray powder diffraction patterns confirmed substitution of the larger cations. The diffraction patterns were also typified by line-broadening and a decrease in the rhombohedral splitting at all doping levels. The dielectric constant of LaAlO[sub 3] was unchanged for all of the fluoride-containing systems and for the 5% Sr,Ti- and Sr,Zr-systems.« less